Brain structural and cognitive correlates of clock drawing performance in Alzheimer's disease

The Clock Drawing Test (CDT) is widely used in the assessment of dementia a nd is known to be sensitive to the detection of deficits in neurodegenerati ve disorders such as Alzheimer's disease (AD). CDT performance is dependent not only on visuospatial and constructional abilities, but also on concept ual and executive functioning; therefore, it is likely to be mediated by mu ltiple brain regions. The purpose of the present study was to identify comp onent cognitive processes and regional cortical volumes that contribute to CDT performance in AD. in 29 patients with probable AD, CDT performance was significantly related to right-, but not left-hemisphere, regional gray ma tter volume. Specifically, CDT score correlated significantly with the righ t anterior and posterior superior temporal lobe volumes. CDT scores showed significant relationships with tests of semantic knowledge, executive funct ion, and visuoconstruction, and receptive language. These. results suggest that in AD patients, CDT performance is attributable to impairment in multi ple cognitive domains but is related specifically to regional volume loss o f right temporal cortex.